3g0h

About this Structure
3G0H is a 2 chains structure of sequences from Homo sapiens. Full crystallographic information is available from OCA.

DDX19 (residues 60-467 visible here of 479 total) is seen here with with a non-hydrolyzable ATP analog (ADPNP) and an mRNA mimic (~6 nts seen of 10-nt poly-U chain) bound. .

DDX19 is made of 2 RecA-like helicase domains (also called the N-terminal ATPase and C-terminal helicase domains in the paper).
 * With RNA and the ATP analog bound, the N-terminal extension (dark green) is tucked at the side and the two domains are close together.
 * This conformation is presumed to resemble the pre-hydrolysis state in which RNA is bound. It is also referred to as the closed state and closed cleft conformation.
 * This scene is similar to the view in Figure 1C of the paper describing the structure.

Showing the structure of DDX19 with RNA and an ATP analog along with the structure where ADP is bound.
 * This overlay clearly illustrates the dramatic shift in the location of the N-terminal extension (dark green).
 * This view clearly shows how the N-terminal helix of the extension extends from the RNA-binding site to down near the ATP-binding site.

Pre-hydrolysis (RNA and ATP bound) to post-hydrolysis (ADP bound) morph. The placement of the N-terminal extension between the two helicase domains negatively regulates ATPase activity. A morph of the ADP-bound structure transitioning to the structure with a the ATP analog and mRNA mimic bound shows the N-terminal extension moves out of the way, closing the cleft to allow formation of a functional ATPase site.
 * Of particular note is arginine 429, the so-called arginine finger, that is essential for ATPase activity. In the RNA and ATP analog- bound structure arginine 429 is near the nucleotide-binding site for ATPase function.
 * Watching arginine 429 during the morph transition illustrates how it is moved away from the active site when RNA is not bound and hydrolysis has occurred to produce ADP.
 * Keep in mind the intermediate models, in between the endpoints, are hypothetical.

Reference
Page originally seeded by OCA on Wed Apr 29 20:54:05 2009